Ignoring copy constructors when figuring out how to create objects, re: issue #9

Author: SteveWilkes

AgileMapper.UnitTests/WhenMappingToConstructors.cs

@@ -83,12 +83,22 @@ public void ShouldIgnoreConstructorsWithNoUseableDataSource()
             result.Value2.ShouldBeDefault();
         }
 
+        // See https://github.com/agileobjects/AgileMapper/issues/9
+        [Fact]
+        public void ShouldIgnoreACopyConstructor()
+        {
+            var source = new CopyConstructor { StringValue = "Copy!" };
+            var result = Mapper.Map(source).ToANew<CopyConstructor>();
+
+            result.StringValue.ShouldBe("Copy!");
+        }
+
         #region Helper Classes
 
-        // ReSharper disable once ClassNeverInstantiated.Local
+        // ReSharper disable ClassNeverInstantiated.Local
+        // ReSharper disable UnusedMember.Local
         private class MultipleConstructors<T1, T2>
         {
-            // ReSharper disable UnusedMember.Local
             public MultipleConstructors()
             {
             }
@@ -103,13 +113,29 @@ public MultipleConstructors(T1 value1, T2 value2)
                 Value1 = value1;
                 Value2 = value2;
             }
-            // ReSharper restore UnusedMember.Local
 
             public T1 Value1 { get; }
 
             public T2 Value2 { get; }
         }
 
+        private class CopyConstructor
+        {
+            public CopyConstructor()
+            {
+            }
+
+            public CopyConstructor(CopyConstructor otherInstance)
+            {
+                StringValue = otherInstance.StringValue;
+            }
+
+            // ReSharper disable once MemberCanBePrivate.Local
+            public string StringValue { get; set; }
+        }
+        // ReSharper restore UnusedMember.Local
+        // ReSharper restore ClassNeverInstantiated.Local
+
         #endregion
     }
 }

AgileMapper/ObjectPopulation/ComplexTypes/ComplexTypeConstructionFactory.cs

@@ -97,6 +97,7 @@ private static void AddNewingConstruction(ICollection<Construction> construction
 
             var greediestAvailableConstructor = mapperData.InstanceVariable.Type
                 .GetPublicInstanceConstructors()
+                .Where(IsNotCopyConstructor)
                 .Select(ctor => CreateConstructorData(ctor, key))
                 .Where(ctor => ctor.CanBeConstructed)
                 .OrderByDescending(ctor => ctor.NumberOfParameters)
@@ -117,6 +118,13 @@ private static void AddNewingConstruction(ICollection<Construction> construction
             constructions.Add(greediestAvailableConstructor.Construction);
         }
 
+        private static bool IsNotCopyConstructor(ConstructorInfo ctor)
+        {
+            // If the constructor takes an instance of itself, we'll potentially end 
+            // up in an infinite loop figuring out how to create instances for it:
+            return ctor.GetParameters().None(p => p.ParameterType == ctor.DeclaringType);
+        }
+
         private static ConstructorData CreateConstructorData(ConstructorInfo ctor, ConstructionKey key)
         {
             var mapperData = key.MappingData.MapperData;